Durbin’s bill comes as Democrats are taking an increasingly closer look at so-called inversions, when U.S. companies change their legal address and often slash their tax bill.

Walgreen’s, the pharmacy chain based in Durbin’s home state of Illinois, is considering a move to Switzerland. Congressional interest in inversions bubbled up again after the U.S. drug maker Pfizer tried to take over AstraZeneca, its British counterpart.

Republicans say that the Democratic interest is misguided, and that lawmakers should instead concentrate on lowering the U.S. corporate tax rate to give companies incentive to stay.